Future hurricanes could heat up Hampton Roads

A year ago, Irene chugged up the coast from North Carolina, a Category 1 hurricane that weakened to a tropical storm by the time she hit Hampton Roads.

Hatches were battened down, generators purchased, store shelves picked clean. Residents of flood-prone areas were evacuated. The U.S. Navy ordered its Second Fleet out to sea from Naval Station Norfolk. Businesses closed, classes were canceled, the community braced.

Irene huffed and puffed through the night of August 27, then cleared out early the next morning on her way to New England, leaving behind power outages, flooding and fallen trees. One of those trees toppled onto an apartment in Newport News, killing an 11-year-old boy inside.

But, other than that isolated tragedy, Hampton Roads breathed a collective sigh of relief: It could've been worse, residents said.

The question raised by climate science is whether it will be worse in future, particularly for Hampton Roads. Whether climate change and global warming — which could spur more intense hurricanes — coupled with our region's rising sea levels and sinking coastline, put people and property here at greater risk than in other parts of the country.

"That's something locally that people are very concerned about," said John Murray, senior scientist at NASA Langley Research Center in Hampton.

Heat engine to hurricane

This is peak season for hurricanes in the Atlantic, and Tropical Storm Isaac — projected to grow into a hurricane early Tuesday as it beelines for New Orleans — is a prime example.

Experts say the physics of how a hurricane forms is complex, but what it strips down to is they're basically heat engines. They need two conditions to form: ocean water warming to about 80 degrees F and light winds aloft.

First, a tropical wave moves across the warm water, creating a thunderstorm. The thunderstorm releases heat energy that can begin to grow and spin, cycling air in a chimney effect. If there are no strong winds aloft to break up that chimney, the system cycles condensation over and over until the heat engine grows into a hurricane.

As temperatures heat up around the planet, climate models project "substantial warming in temperature extremes" by the end of this century, according to the Summary for Policymakers released last year by the Intergovernmental Panel on Climate Change. The panel was established by the United Nations and the World Meteorological Organization in 1988 to study climate change and its impact.

The summary also notes that heavy rainfalls associated with tropical cyclones, or hurricanes, are "likely to increase with continued warming," as are the average maximum wind speeds.

It's less clear if the Hampton Roads region will see a greater number of hurricanes in future. Local climate experts caution that climate models projecting out 50 to 100 years show mixed results.

"They get some strengthening of hurricanes," said Bruce Wielicki, a global warming expert at NASA Langley. "But you can't yet claim there's going to be a larger number of them."

Potential for more damage

But even if the intensity and frequency of hurricanes that hit locally remain the same, there's another critical factor to consider: Sea level is rising, placing the region at even greater risk from the flooding that hurricanes inflict.

In fact, the sea level along the East Coast is rising three to four times faster than anywhere else on the planet, according to a U.S. Geological Survey report issued in June. Since 1990, global sea levels have risen about 2 inches. In Norfolk, meanwhile, they climbed 4.8 inches.

The report attributes regional variations in rise to differences in land movements, changes in ocean currents, water temperatures and salinity. Feeding the overall rise are melting ice caps and glaciers, plus the natural expansion of seawater as it warms. Computer models estimate global sea levels could increase by as much as 3.3 feet by 2100. Along the East Coast, the rise could be nearly a foot higher.

But Hampton Roads has a third critical factor working against it: Its coastline is sinking, which is believed to be either an after-effect of an ancient asteroid that landed in the Chesapeake Bay or the region's crust still adjusting to the last Ice Age.

All these factors, along with increased coastal development, combine to form a perfect storm of risk for the region.

"The area of greatest certainty is that if you have warmer ocean waters, you're likely to have more intense storms," said David Malmquist, spokesman at the Virginia Institute of Marine Science (VIMS) in Gloucester Point. "Another area of certainty is the fact that sea level is rising, and with higher sea level you're more likely to have damage on land with any kind of hurricane."